A bicontinuous mesophase geometry with hexagonal symmetry

Network Phases with Multiple-Junction Geometries at the Gyroid-Diamond Transition

A novel phase sequence for the transition from the double diamond to the double gyroid cubic phases via two non-cubic intermediate phases, an orthorhombic Fmmm (O⁶⁹) phase and a hexagonal P6₃/m (H¹⁷⁶) phase, is reported for specifically designed bolapolyphiles composed of a linear rod-like bistolane core with sticky glycerol ends and two branched central and two linear peripheral side chains. These liquid crystalline (LC) phases represent members of a new class of unicontinuous network phases, formed by longitudinal rod bundles with polar spheres acting as junctions and the alkyl chains forming the continuum around them. In contrast to previously known bicontinuous cubic networks, they combine different junctions with different angles in a common structure, and one of them even represents a triple network instead of the usually found double networks. This provides new perspectives for the design of soft network phases with enhanced structural complexity, inspiring the search for new supramolecular networks, nano-particle arrays, and photonic band-gap materials.

Mapping the Impact of a Polar Aprotic Solvent on the Microstructure and Dynamic Phase Transition in Glycerol Monooleate/Oleic Acid Systems

OBJECTIVES

The impact of incorporating a polar aprotic solvent, dimethyl sulfoxide (DMSO), in glycerol monooleate/oleic acid systems was evaluated briefly to map its influence on the gel microstructure and dynamic phase transition in controlling the performance of a polyene antifungal drug delivery system.

MATERIALS AND METHODS

An in situ gelling fluid precursor system (IGFPS) exhibiting inverse lyotropic liquid crystalline phases was developed by simple solution add-mixture method. Polarized light microscopy, small angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and oscillatory rheological assessments were performed to ascertain microstructural modulations. The developed system was examined for minimum gelling volume, gelling time, swelling behavior, mucoadhesion, in vitro antifungal activity, and in vitro drug release.

RESULTS

The SAXS study identifies the coexistence of Im3m cubic phase with HCP P63/mmc hexagonal structures. The SAXS and DSC data highlight DMSO's unique ability to work both as a kosmotropic or chaotropic solvent and to be a function of its concentration. The in vitro antifungal test results indicate the concentration of DMSO to be a controlling factor in drug release and diffusion. The in vitro drug release kinetic studies reveal that most of the gel samples follow the matrix model and anomalous type release as implied by Peppas model.

CONCLUSION

Finally, the antifungal IGFPS formulated was found to have the required low viscosity, responsive sol-gel phase transition, appreciative mechanical properties, and desirable antifungal effect with sustained drug release performance.

Tunable Self-Assembly of Diblock Copolymers into Colloidal Particles with Triply Periodic Minimal Surfaces

We herein report the tunable self-assembly of simple block copolymers, namely polystyrene-block-poly(ethylene oxide) (PS-b-PEO) diblock copolymers, into porous cubosomes with inverse Im3‾m or Pn3‾m mesophases of controlled unit cell parameters as well as hexasomes with an inverse hexagonal (p6mm) structure, which have been rarely observed in polymer self-assembly. A new morphological phase diagram was constructed for the solution self-assembly of PS-b-PEO based on the volume fraction of the PS block against the initial copolymer concentration. The formation mechanisms of the cubosomes and hexasomes have also been revealed. This study not only affords a simple system for the controllable preparation and fundamental studies of ordered bicontinuous structures, but also opens up a new avenue towards porous architectures with highly ordered pores.

Reply to the 'Comment on "Discovery of a tetracontinuous, aqueous lyotropic network phase with unusual 3D-hexagonal symmetry"' by G. Schröder-Turk, M. Fischer and S. Hyde

A new calculation by Fischer et al. suggests that the 3etc network phase with 3D-hexagonal symmetry (space group #193: P63/mcm) may be a generic structure adopted by self-assembling soft materials, thereby broadening the context for our recent report of its spontaneous formation in lyotropic liquid crystals. The experimental observation of the 3etc phase further validates previous theoretical models used to predict its stability, provocatively suggesting that other polycontinuous network phases predicted by these methods may be discovered in the future. While these network phase morphologies are often mathematically described in terms of their underlying triply periodic minimal surfaces (TPMS), the numerous potential applications of these functional nanostructured soft materials require the development of a concise, consistent, and unambiguous nomenclature for their complete description. In this comment, we propose adoption of a nomenclature that describes each mesophase more generally in terms of the total number of non-intersecting domains into which three-dimensional space is partitioned.

Discovery of a tetracontinuous, aqueous lyotropic network phase with unusual 3D-hexagonal symmetry

Network phase aqueous lyotropic liquid crystals (LLCs) are technologically useful materials with myriad applications in chemistry, biology, and materials science, which stem from their structurally periodic aqueous and hydrophobic nanodomains (∼0.7-5.0 nm in diameter) that are lined with well-defined chemical functionalities. The exclusive observation of bicontinuous cubic network phase LLCs (e.g., double gyroid, double diamond, and primitive phases) has fueled speculations that all stable LLC network phases must exhibit cubic symmetry. Herein, we describe the self-assembly behavior of a simple aliphatic gemini surfactant that forms the first example of a triply periodic network phase LLC with the 3D-hexagonal symmetry P63/mcm (space group #193). This normal, tetracontinuous 3D-hexagonal network LLC phase HI(193) partitions space into four continuous and interpenetrating, yet non-intersecting volumes. This discovery directly demonstrates that the gemini amphiphile platform furnishes a rational strategy for discovering and stabilizing new, three-dimensionally periodic multiply continuous network phase LLCs with variable symmetries and potentially new applications.

Lipid crystallization: from self-assembly to hierarchical and biological ordering

Lipid crystallization is ubiquitous in nature, observed in biological structures as well as in commercial products and applications. In a dehydrated state most of the lipids form well ordered crystals, whereas in an aqueous environment they self-assemble into various crystalline, liquid crystalline or sometimes macroscopically disordered phases. Lipid self-organization extends further to hierarchical levels including structured emulsions and nanostructured particles. Many consumer products including cosmetics, foods and medicines account for such lipid architectures. Cell membranes primarily consist of planar lipid bilayers; however sub-cellular biomembranes are more of a convoluted type. Some of the biological entities have lipids in truly crystalline form; yet liquid crystalline lipid phases are prevalent, in general. Crystallization of fats - triglyceride lipids - has been relatively well documented and reviewed more often, but this review features other areas where lipid organization is crucial and diverse. Some recent advances along with a few explicit examples of model lipid phases and biological evidences are also reported.

Tensorial Minkowski functionals of triply periodic minimal surfaces

A fundamental understanding of the formation and properties of a complex spatial structure relies on robust quantitative tools to characterize morphology. A systematic approach to the characterization of average properties of anisotropic complex interfacial geometries is provided by integral geometry which furnishes a family of morphological descriptors known as tensorial Minkowski functionals. These functionals are curvature-weighted integrals of tensor products of position vectors and surface normal vectors over the interfacial surface. We here demonstrate their use by application to non-cubic triply periodic minimal surface model geometries, whose Weierstrass parametrizations allow for accurate numerical computation of the Minkowski tensors.